In the control of heavy duty internal combustion engines, the conventional practice utilizes electronic control units having volatile and non-volatile memory, input and output driver circuitry, and a processor that executes instructions to control the engine and its various systems and sub-systems. A particular electronic control unit communicates with numerous sensors, actuators, and other electronic control units to control various functions, which may include various aspects of field delivery, transmission control, and many others. When the engine includes a variable speed fan, the electronic control unit operates the fan in accordance with received fan request signals. Typically, although variable speed fans have been used with internal combustion engines, the control schemes utilized to control the variable speed fans have been simple and quite conservative to reduce the possibility of accidental overheating and engine component failure.
However, the heavy duty engine business is extremely competitive. Increased demands are being placed on engine manufacturers to design and build engines that provide better engine performance, improved reliability, and greater durability while meeting more stringent emission and noise requirements. Along with all of these, perhaps the greatest customer demand is to provide engines that are more fuel efficient. Demands for fuel efficiency are becoming so great, that all engine driven systems in the vehicle are being scrutinized in attempts to reduce power consumption when possible.
For the foregoing reasons, there is a need for an improved method of controlling an internal combustion engine including a variable speed fan in which the variable speed fan is aggressively controlled to improve vehicle fuel efficiency.